What's up with my RF

[emaN]

looks like erik & shaun are onto it...
hope you get it sorted bro...

(i'll check that "5 degrees past vertical" tonight )

[F5 Dave]

Suzukis GSXRs & Derivatives do have issues with coils, but pull the plugs & check if any look like they are considerably blacker than the others. Here is a bad picture of an emulsion tube I pulled out of my RF a couple of weeks back.

What you can see if you squint & imagine it after I've subliminally suggested it through mind damaging thought control (sorry) is it is ovalised & can even see swarf.

[riffer]

I've been on the phone to Frosty tonight, and gradually pulling the bike apart and testing things.

Not the plugs.
Not the coils.
Not the low tension leads.
Not the high tension leads.
Not any gunk in the float bowl either.

Here's the problem. And I didn't work it out until I decided I was going to have to strip number 1 carb and blow out the pilot jet, which both Frosty and I decided was the problem.

And I pulled off the airbox, and blow me down, there's something rattling around in it. It drops to the ground and looks suspiciously like a javelin head. Bugger me, that's gotta be a jet needle, says I.

And wouldn't you know it. The bloody jet needle's broken off in number 1 carbie and most of it (I hope) has found its way into the airbox.

Check out the pics. Father in Law will be pillioning me to work tomorrow.

Now I've NEVER heard of this happening before. But I stand ready to be corrected on this.

[Motu]

I've never seen a needle break either,there is just no stress on them in that direction to cause a break.So either at some point in time it has undergone some stress in that plane,or there is a manufacturing fault.

[Ixion]

I've seen it. Only once . There is stress on them the air flow past them can actually induce some considerable stresses, under certain circumstances they can actually vibrate

[Motu]

Yes,could certainly do that.When SU got rid of the fixed needle and went to a floppy floating needle there was some jet wear,they would make the jet oval.So if the needle didn't have enough spring tension on it it could set up a vibration, a certain frequency could induce a failure for sure.

[riffer]

What you can't see from the photos is the wear on the needle.

Looking sideways at the end that was still stuck in the diaphragm, you can see that there's been some wearing and its actually nearly worn to half its diameter on one side. I'm thinking that the gradual wear of the needle going up down the emulsion tube has caused it to fail right at the point where the wear stopped as there's a clean break there.

So, I can get a new needle, but its got me wondering. The RF's have a reputation for ovalising their emulsion tubes (if that's what I think they are - looking at the service manual Suzuki call it a needle jet). Is it possible that worn emulsion tubes would cause this kind of wear?

Damn. Its 11.00 and too late to go back out to the gargre but I really want to pull the diaphragm caps off the other carbies and have a damn good look at the needles on those as well...

Something for tomorrow. I wonder if Wellington Motorcycles will have a new jet needle in stock...

[Fatjim]

Another farkin suxuki craps itself while following a Ducati!

Glad it's sorted mate. That is one pain in the arse fault.

May be cheaper to get a dynojet rejetting kit, probably a good idea to do all the carbies at the same time.

[Ixion]

The needle moves in the needle jet (aka emulsion tube) . The movement wears the jet. But obviously if the needle rubbing on the jet wears the latter, the needle must also wear.

So it is likely that all the needles and all the jets are worn. Replacement should improve fuel economy , engine smoothness and maybe power.

[riffer]

Engine Smoothness?

You've never ridden an RF have you Ixion?

Actually, it's been a bit rougher than usual lately. I guess its just sneaked up on me.

Money, as usual, will be the final arbiter on this one. This close to Xmas I'm betting it will be the replacement of the needle unfortunately.

I'll put the full rejet on the to-do list. Actually, F5 Dave - you've just done this - what's the damage for all four carbies?

[Motu]

How loose are the needles? If you can find some way to firm up their seating they may not move around enough to contact the needle jet (the more common term for this part) After all there have been millions upon millions of bikes that haven't had this sort of wear....something is wrong with the initial design - rectify Suzuki's fuck up.

[Ixion]

Thing is, if you lock 'em down, you're going to have to make sure they're centralised in the jet, and in exactly the same plane. I suspect this is why they are designed loose, so Suzuki (OK, Mikuni or whoever) didn't need to worry about getting them concentric with the jet.

[riffer]

Well, I showed the needle to the head mechanic at WMCC (can't remember his name). He says he's seen it before in RFs.

His explanation is it's caused by negative/positive air pressure in the carb causing the needle to go back and forth while going up and down. Apparently there's some kind of design problem in this carb that causes the needle to flutter a bit.

[Motu]

Apparently there's some kind of design problem in this carb .

And like how many millions of carbs has this company designed and produced without any problems of this sort? They must of given the job to some kid fresh out of design school - all those old guys didn't know what they were doing huh?

[F5 Dave]

I have some spare needles you can have, erm, somewhere, I'm shifting this weekend so they are in a box, but I think I know which one.

Check the emulsion tube (needle jet sorry) it runs in too as said.

Yams with similar carbs have same issues. Many bikes do, 'parently.